School build four-stroke model engine 

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សួរស្ដី

lol cringe

Cringe

There is no way to fit an exhaust at the moment. I could change it, but probably won't. The students who made this are gone now, so it's more likely I would just design a new engine for another class to make.

@@slome815 awesome, i appreciate it

@@slome815 maybe you have draws or other files with dimensions? I want to make engine like this with valves that are outside. Maybe You can share some files with me?

@@misterhash9329 I do have inventor files, I could convert them to step or iges and send them.

Or just send me inventor files to save Your time :)

សួរស្ដី

Maybe the cam was salvaged from a scrap engine by shortening it

You will have to add an ignition system and carburettor. I never designed an ignition system, we just added it quickly with parts laying around, more or less as an afterthought. The "jampot" vapour carburettor works well and is really hard to mess up, it's also very fast to make.

@@slome815 Thank you so much for replying to me. I really appreciate your feedback and input. I will document the build and credit you in any posts I make. Thank you again. Cheers Aaron (Melbourne Australia).

It is not a scaled up version. It's just a basic fourstroke I designed. As for the bore and stroke, I think it's 30mmx30mm. The CAD model is available on grabcad in case you're interested.

@@slome815 many thanks, I will check the cad out

Im trying to build my own, but I don't know what to do about the ignition system. Any help is welcome

It's just a microswitch we had laying around. I didn't include it in my drawing, and it was fitted more or less as an afterthought. The rest of the ignition system is an electronic ignition set from "velleman", with the coil from an old car. There are multiple electronic ignition systems out there, this is a bulky system, but if you look at ignition systems for model airplanes you should be able to find a more compact one.

@@slome815 Thanks a lot!

I believe the nut "valve" on the jar controls how much fuel-air mixture goes into the engine and thus in turn regulates how fast the fuel can burn and in turn how fast the piston cycles.

It has no piston rings, just a really good fit. The clearance is in the 1-5µm range. We realised that the oil probably won't get to the engine, but put oil in the gasoline anyway. Strange enough there doesn't seem to be an oil film left in the carburettor/gas tank when it runs out of gas, so maybe some of it does get to the engine. Anyway, the oil used to lubricate the intake valve does into the cylinder, and should be enough to lubricate it.

No lubrication system in this engine, the cylinder walls are not being lubricated like in a normal 4 stroke where the crank case stores oil.

This even used to be done in cars for the running in period. In dutch it's called "bovensmering" when done in a fourstroke engine, no idea what the proper english term wouid be.

Since this was build by students It took a long time. I'm guessing around 600 build hours total. I think If you have some experience with a lathe and milling machine you could probably build it in about 100 hours. Probably a good bit less when you have a CNC machine.

The pistons were made to have piston rings. But because of a lack of time the the engine is now running without them. This is possible because the clearance between the piston and cylinder is very small, somewhere between 5-20µm. If you want to make piston rings, you first turn the outside and inside diameter to tolerance, then part the ring off on the lathe, split it, put a spacer between the gap, heat it to 800° (it then keeps the gap and acts like a spring) and then grind the gap.

@@slome815 Thank you. I will try it with piston rings. Is it okay to still have about 20 micron clearance or should it be more when using rings?

@@CrankAndCraft It should be fine as long as you use cast iron for both the cylinder and pistons.

The compression ratio is about 5. It runs on either white gas, 95 or 98. It really doesn't matter at such a low compression ratio.

It is open crankcase, which is pre-lubricated before running. Many old (vintage) engines had this design back in the day.

Hey mate, Sander has kindly provided the weblink to 3D CAD files to the description area. It's "grab cad link".

Still a four stroke. Just valve lubrication. It used to be required during the run in period of many cars before the 60's as well.

It mixes air and fuel, thus a carburettor. It was even used on some early cars. The name used then was surface carburettor.

Large gear has 44 teeth and the small gear has 22 teeth

Large gear has 44 teeth and the small gear has 22 teeth

Look at camshaft gear ratio...

the fact it has a cam = 4 stroke

Can't you see the valve system?

We couldn't get it to work with a real carb. It's 22cc, but the low rpm's mean it has a very low air intake compared to commercial 20-25cc engines. You would really need a tiny carburettor.

@@slome815 you could take a carb from a weed eater. It would be small enough to work

@@slome815 What about a small RC engine carburetor, I mean one for a 2.5-5cc engine or something like that.

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សួរស្ដី

This is not a kit. All of the parts were made either on conventional lathes and milling machines or CNC machines. The base was made as a 3Dprinted model and then sand cast in aluminium. Only the ignition system is a kit.

not for sale smh my head idiot

@@armoredmicrobe2939 RIP in peace, dude

@@55parkerb I suspect @MrStealYoGirl is too dim to appreciate your response.

Nope.

U added oil with fuel

Bruh